-LRB- CNN -RRB- -- Besides charting the nature of space and time and penning the bestseller `` A Brief History of Time , '' Stephen Hawking has another distinction : He beat the life-expectancy odds for people with ALS , amyotrophic lateral sclerosis .

Stephen Hawking , shown in Pasadena , California , in March , is hospitalized but said to be `` comfortable . ''

Most people with ALS survive only two to five years after diagnosis . Hawking , on the other hand , has lived more than 40 years since he learned he had the disease , which is also known as Lou Gehrig 's Disease in America and motor neuron disease , or MND , in the United Kingdom .

Hawking , 67 , was taken to Addenbrookes Hospital in Cambridge , England , on Monday in a `` very ill '' condition , and spent the night in the hospital . He was said to be `` comfortable '' Tuesday .

Bob Hawkins , 75 , of Fayetteville , North Carolina , who learned of his ALS diagnosis last year , said Hawking , with his long life and ability to communicate through a voice synthesizer , gives him hope . The physicist should be a role model for people with the disease as well as those without it , Hawkins said .

`` The man is brilliant , and he has striven through a lot of adversity to accomplish all of the things he has accomplished , '' Hawkins said . `` He should be an inspiration for anyone . ''

The British physicist also embodies the idea of empowering people with ALS to live life to the fullest , said Dr. Lucie Bruijn , scientific director for the ALS Association , in an e-mail . This empowerment theme is part of the mission of the ALS Association , she said .

`` To have achieved so much in his lifetime while battling Lou Gehrig 's Disease is quite remarkable , '' she said .

ALS affects nerve cells in the brain and spinal cord , which results in muscle weakness and atrophy . The disease causes the death of motor neurons , meaning the brain loses its ability to control muscle movement .

Hawking has had direct involvement in promoting awareness and research into his disease . He recently agreed to be a patron of the MND Association in Northampton , England , meaning he will lend his name to the charity and support it by attending events , fundraising , or other activities .

He has participated in some of the organization 's high-profile events , said Mel Barry , communications manager at the MND Association .

`` He 's a very busy man , so it 's wonderful that he 's publicly supporting us with his very heavy workload , '' she said .

Hawking 's case is also unusual because his condition was diagnosed at a young age , said Sharon Matland , vice president of patient services at the ALS Association . People typically are between 40 and 70 when they learn they have ALS ; Hawking found out at age 21 . Some very rare cases manifest in the late teens , Bruijn said .

There have been other rare cases of people living long lives with ALS , although none as famous as Hawking . Barry said she knows of a man in Ireland who has lived with the disease for 30 years -- but only about 5 percent of people with ALS live longer than 10 years .

ALS affects 350,000 people worldwide and up to 30,000 people in the United States , the ALS Association estimates .

`` It totally upsets your entire way of living , '' Hawkins of North Carolina said . `` It slowly takes over your entire muscle structure and eventually your limbs are affected , your speech may or may not be affected . The only part of your body that is n't affected is your mind . ''

Still , patients experience different symptoms , and some do have cognitive impairment , Matland said . They may have trouble making day-to-day decisions , such as choosing which bills to pay first .

Hawkins said he first experienced weakness in his legs and arms , typical symptoms of the disease . People with ALS may also find it difficult to lift their arms or feet , Matland said .

`` You drop things or you ca n't grasp things as you might have been able to do in the past , '' she said .

Loss of voice is another potential symptom , but some people are able to speak until they die , Barry said . The nature of the disease is that it 's very different in each person , she said .

Most people with ALS become dependent on a wheelchair -- sometimes within six to eight months , but the time frame varies , Matland said . Typically , the ultimate cause of death is respiratory failure , because ALS affects the muscles used for breathing , she said .

David Niven , the English actor known for his roles in `` Around the World in 80 Days '' and `` The Pink Panther , '' died of ALS at age 73 . He suffered from the disease for more than a year .

A variety of ongoing clinical trials seek to find an effective treatment for ALS in the U.S. Drugs in these trials include lithium , ceftriaxone , and memantine , according to the ALS Association . A recent study showed there may be a genetic component to the disease .

In the UK , the MND Association is funding a trial for lithium , which has produced promising results in mice , Barry said . Psychiatrists currently prescribe lithium , a mood-stabilizing drug , for bipolar disorder and other conditions .

An FDA-approved drug called riluzole has been shown to prolong survival for some ALS patients , but extends the life span by only three to six months , Barry said . Typically , palliative care is the main treatment -- managing symptoms rather than stopping or curing them .

Stem cell therapy may hold promise for the disease , but the general perception is that research into it is not sufficiently advanced , according to the MND Association .

To raise money for research in the U.S. , the ALS Association hosts walks across the country . Hawkins said he will be participating in the 2009 Fayetteville , North Carolina , Walk to Defeat ALS in May .

`` I would encourage everyone to recognize how terrible this disease is , and encourage them to support the ALS Association and research projects , '' he said .

CNN 's Jennifer Pifer Bixler contributed to this report .

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Stephen Hawking is a rare case of someone who has survived decades with ALS

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ALS affects 350,000 people worldwide and as many as 30,000 people in the U.S.

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Symptoms vary from person to person ; some lose their speech but others do not

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Clinical trials are in progress for a variety of treatments